The Morin Partial Stroke Test Device (PSTD) was developed to allow users to test emergency shut-down valves without disrupting the process. The PSTD unit is locked out when the unit is in service and the valve functions normally. When the unit needs to be tested, the operator unlocks the device and inserts the stop pin, allowing for 15 degrees of valve travel to sufficiently test the valve package. Unlike electronic versions, you are guaranteed a hard stop and no over-travel, time after time, without any special calibration.